Psoriasis: childhood psoriasis

Approximately four percent of all skin conditions diagnosed in children under 16 are attributed to psoriasis. Although the most common presentations of psoriasis in children are chronic plaque psoriasis and scalp psoriasis, diagnosing childhood psoriasis can be difficult.

This chapter is set out as follows:

• The natural history of psoriasis in children is difficult to predict
• Even if a child has bad psoriasis it does not mean that they will continue to have psoriasis as an adult
• Children with psoriatic arthritis tend to have a worse prognosis

It is estimated that if any two of the seven following criteria are present, this will correctly identify the diagnosis in 78% of of children with psoriasis:

• Scale and erythema in the scalp involving the hairline
• Scaly erythema inside the external auditory meatus
• Persistent well-demarcated erythematous rash anywhere on the body
• Persistent erythema in the umbilicus
• Scaly erythematous plaques on the extensor surfaces of the elbows and/or knees
• Well-demarcated erythematous rash in the napkin area involving the crural fold
• Family history of psoriasis

The following are more commonly found in children compared with adults:

• Distribution
• Face, especially eyes and ears
• Scalp - may be the only presenting feature
• Distal limbs 
• One digit - often associated with paronychia and nail changes. Often recalcitrant to treatment, but many improve with time

• Increased incidence of guttate psoriasis 
  • The natural history of guttate psoriasis is that while some patients get one or two outbreaks and do not go on to develop psoriasis in adult life, in others the psoriasis persists. Refer to the chapter Guttate psoriasis

• 'Nappy rash' / genital involvement
  • It is likely that some infants previously diagnosed as having seborrhoeic dermatitis of the nappy area, turn out instead to have psoriasis

• An eczematised form of psoriasis 
  • The two problems may co-exist

• Morphology of chronic plaque psoriasis 
  • Lesions tends to be paler with less scale, although still well-demarcated

• Many of the same treatments used in adults are used in children - refer to the chapter Chronic plaque psoriasis